This application claims priority to EP/01109198.0, filed Apr. 12, 2001 under the European Patent Convention and which is incorporated by reference herein in its entirety.
The invention relates to a gas turbine having a ring of stator blades and a ring of rotor blades in a gas duct, and having a casing and funnel-like guide parts which are secured against rotation therein and are axially mutually displaceable, as carriers for rings forming an outer jacket of the gas duct.
Gas turbines are often acted on by changing loads, not only during their starting phase but also during continuous operation. The result is nonsteady-state operation, in particular also with regard to the temperatures assumed by the individual components. In order to avoid damage to the turbine, the individual components are therefore usually clamped in in such a way that they can execute thermally induced dimensional changes without hindrance.
In order largely to minimize turbine losses resulting from cross flows over the tips of their rotor blades, the smallest possible radial gaps have to be maintained between the tips of the rotor blades and the guide surfaces lying opposite the latter. Since both the rotor blades and their rotor and stator blades and their carriers, just like a casing which connects them all, viewed over time expand and/or shrink to a different extent at each load change, an optimal radial gap over the tips of the rotor blades is established only for very few of arbitrarily many steady operating states. The operation of these gas turbines is therefore frequently carried out with a gap width which is not optimized and, therefore, with an efficiency which is not optimized.
U.S. Pat. No. 4,177,004 discloses a turbine configuration in which the tips of the rotor blades themselves remove material from a guide surface lying opposite them, so that for this arrangement, in the operating state in which the tips of the rotor blades approach the guide surfaces to the greatest extent, the rotor blade tip gap virtually disappears. In every other operating state, however, even in this known arrangement, the rotor blade tip gap becomes greater again and therefore less beneficial.
In the case of other previously disclosed arrangements, although it has been possible to keep the thermally induced relative movements of the components low for many operating states by selecting suitable pairs of materials, it is also true there that an optimum rotor blade tip gap in each case prevails only in a specific steady state. In every other state, less beneficial conditions again occur.
The invention is, then, based on the object of developing a gas turbine system in such a way that an optimum rotor blade tip gap is provided in it over a large number of operating states, so that a basic precondition for achieving a good efficiency is ensured.
According to the invention, for a gas turbine of the type specified at the beginning, this object is achieved in that at least one of the funnel-like guide parts can be displaced axially under control by a motor. Expediently, in this case the motor used is a large number of hydraulic presses distributed over the circumference of the guide part. However, any other type of drive is also the content of this invention. The particular advantage of this arrangement lies in the possibility of setting the rotor blade tip gap actively by means of axial movement of the guide part. In the case of restricting the active adjustability to axial movements, use is advantageously made of the conicity provided by the flared or funnel-like shape of the guide part since, because of this conicity, any axial displacement of the same also has the effect of changing the rotor blade tip gap, to be considered substantially radially.
Other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. The drawings constitute part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.